In studies of patients with affective disorders, antidepressant responses to imipramine in females and lithium carbonate in males and females have been found to be significantly correlated with single-day responses to d-amphetamine, supporting a suggestion that an amphetamine test might avoid a 3-4 week drug trial in a potentially non-responsive patient. Other factors identified as capable of affecting the mood responses to amphetamine include depression severity and individual differences in plasa amphetamine levels obtained with a standard dose. Fenfluramine, a drug with predominant serotonergic system effects, has been found to have antidepressant effects, particularly in bipolar patients. Both fenfluramine and amphetamine produce elevations in plasma prolactin concentrations. Lithium carbonate treatment of a patient with hyperparathyroidism and depression has been found to markedly reduce urinary calcium excretion in a dose-dependent fashion. However, in other studies lithium treatment was not found to block the urinary cyclic AMP response to parathyroid hormone administration--an exception to the many other adenylate cyclase responses in other tissues which are inhibited by lithium. Further characterization of psychological elements in depression, particularly in bipolar compared to unipolar patients, have been accomplished using state-dependent learning approaches, behavioral and self-rating scales and standard psychological tests such as the MMPI in attempts to understand and predict individual differences in response to drugs.